Fuel injector assembly

ABSTRACT

A fuel injector assembly for injecting liquid fuel into an internal combustion engine cylinder comprises a main cylinder mounted upon the engine block and a main piston slidable within the main cylinder. The piston has an outer piston face which is exposed to the conditions prevailing in the engine cylinder and an inner piston face. A pump plunger is secured to the inner piston face and coacts with a pump chamber to pump liquid fuel into the engine cylinder during upward movement of the main piston into the main cylinder caused by the progressively increasing pressure developed in the engine cylinder during the compression stroke of the engine piston. Liquid fuel is also admitted into the interior of the main cylinder behind the main piston so that the increase in pressure developed in the engine cylinder acts through the main piston to accordingly pressurize the liquid fuel within the main cylinder. A pressure-responsive modulator valve modulates the exhausting of fuel from the main cylinder in dependence upon the fuel pressure within the main cylinder to thereby control the rate and extent of movement of the main piston to accordingly control the timing and amount of fuel injected into the engine cylinder.

United States Patent 5] Aug. 12, 1975 Malpass, Sr.

[ 1 FUEL INJECTOR ASSEMBLY [76] Inventor: Alexander Malpass, Sr., 5131 Carolina Beach Rd., Wilmington, NC. 28401 [22] Filed: May 24, 1973 [21] Appl. No.: 363,423

[52 US. Cl. 123/139 AJ; 123/139 AM; 239/533 [51] Int. Cl. F02m 49/02 [58} Field of Search... 123/139 R, 139 AM, 139 A]; 239/533 [56'] References Cited UNITED STATES PATENTS 1,995,459 3/1935 Olsen 123 139 AJ 2,203,669 6/1940 Butler.... 123/139 AJ 2,598,528 5/1952 French 123/139 AJ 2,74Q,667 4/1956 Dickson et al.. 123/139 AJ 2,799,263 7/1957 French 123/139 AJ 3,236,219 2/1966 Bilisco 123/139 AJ FOREIGN PATENTS OR APPLICATIONS 565,429 11/1944 United Kingdom 123/139 AJ Primary Examiner-Charles .I. Myhre Assistant ExaminerTony Argenbright [5 7] ABSTRACT A fuel injector assembly for injecting liquid fuel into an internal combustion engine cylinder comprises a main cylinder mounted upon the engine block and a main piston slidable within the main cylinder. The piston has an outer piston face which is exposed to the conditions prevailing in the engine cylinder and an inner piston face. A pump plunger is secured to the inner piston face and coacts with a pump chamber to pump liquid fuel into the engine cylinder during upward movement of the main piston into the main cylinder caused by the progressively increasing pressure developed in the engine cylinder during the compression stroke of the engine piston. Liquid fuel is also admitted into the interior of the main cylinder behind the main piston so that the increase in pressure developed in the engine cylinder acts through the main piston to accordingly pressurize the liquid fuel within the main cylinder. A pressure-responsive modulator valve modulates the exhausting of fuel from the main cylinder in dependence upon the fuel pressure within the main cylinder to thereby control the rate and extent of movement of the main piston to accordingly control the timing and amount of fuel injected into the engine cylinder.

2 Claims, 7 Drawing Figures 42 23 hzz SHEU PATENTEB AUB I 21975 PATENTED AUG I ZISYS SIIEEI FIG. 30

FIG. 38

FIG. 3A

FIG.

FIG.

FUEL INJECTOR ASSEMBLY The present invention pertains generally to fuel in jectors and more particularly to fuel injector assemblies for injecting fuel into the combustion chambers of high speed internal combustion engines.

It has long been an objective in the automotive industry to'develop a fuel injection system for high speed internal combustion engines operating at speeds of 3000 rpm and higher. Motor vehicles equipped with such internal combustion engines operate'in varying environments and under diverse weather conditions and therefore efficient and adaptable fuel injection systems are needed to obtain proper control of fuel-air mixture ratios and to ensure complete and efficient fuel combustion under various combustion pressures.

It is therefore a primary object of the present invention to provide a fuel injector assembly for injecting a metered amount of fuel into internal combustion engine cylinders in dependence upon the engine requirements.

It is a further object of the present invention to provide a fuel injector assembly for injecting fuel into internal combustion engine cylinders and which automatically compensates for variations in air density.

It is yet another object of the present invention to provide a fuel injector assembly which utilizes all hydraulic components and thus is fast acting and reliable in operation.

It is still a further object of the present invention to provide a fuel injector assembly for an internal combustion engine which is simple and durable in construction and which can be manufactured and maintained at a reasonable cost.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the present invention comprises the combinations and arrangements of parts illustrated in the presently preferred embodiments of the invention which are hereinafter set forth in sufficient detail to enable those persons skilled in the art to clearly understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings, wherein like reference characters denote like parts in the various views, and wherein:

FIG. 1 is a cross-sectional side view of a fuel injector assembly according to the present invention;

FIG. 2 is a cross-sectional side view similar to FIG. 1 but showing the components in different operating positions;

FIGS. 3A-3C are explanatory views depicting various working positions of a modulator valve which forms part of the fuel injector assembly shown in FIGS. 1 and 2;

FIG. 4 is a cross-sectional side view of another embodiment of fuel injector pump useable in the fuel injector assembly; and

FIG. 5- is a cross-sectional side view of a further embodiment of fuel injector pump useable in the fuel injector assembly.

As seen in FIG. 1 and 2, the fuel injector assembly comprises a main body unit having a generally V- shaped cross-section. At the lower portion of the body unit is provided an hydraulic cylinder 11 having a closed upper end and an open lower end. The fuel injector assembly is mounted in use upon a cylinder head H of an internal combustion engine such that the lower tip of the cylinder 11 extends into the associated engine cylinder C which defines a combustion zone.

A working member is slidably mounted in the cylinder 11 and the working member comprises an essentially hollow piston 13 having a peripheral side wall 14 and a head 15. The piston head 15 has an arcuate or rounded shape and projects slightly from the open end of the cylinder 11 into the engine cylinder C when the piston 13 is situated at the end of its downstroke. The working piston 13 coacts with the cylinder 11 to define therebetween a variable volume control chamber 12.

Biasing means comprising a helically coiled compression spring 17 is disposed within the working chamber 12 and resiliently biases the working piston 13 downwardly to its outermost position. The biasing spring 17 is compressed between the upper end portion of the chamber 12 and a seating flange 18 extending around the interior of the working piston 13.

A fuel injector pump is provided in the main unit body 10 for pumping fuel in a controlled manner into the engine cylinder C. The fuel injector pump consists of a pump chamber 20 in the main body unit 10 which opens into the upper portion of the control chamber 12 and a pump plunger 22 slidably mounted in the pump chamber 20 to define therewith a variable volume pumping chamber. The pump plunger has a cylindrical upper portion 23 having a shape complementing that of the pump chamber 20 and a cylindrical lower portion 24 of larger diameter than the upper portion 23. The lower portion 24 of the pump plunger 22 is secured to the inner face of the piston head 15 so that movement of the working piston 13 effects a corresponding movement of the pump plunger.

A throughbore 25 extends longitudinally through the pump plunger 22 and defines a pump outlet passageway which communicates at its upper end with the variable volume pumping chamber and communicates at its lower end, through a spray nozzle 27, with the interior of the enging cylinder C. A radial bore 26 in the plunger provides communication between the throughbore 25 and the interior of the control chamber 12 and functions in a manner hereinafter described to assist in supplying fuel to the pump chamber 20. The throughbore 25 has an enlarged section within the lower portion 24 of the pump plunger and the enlarged section comprises a valve housing which contains therein a check valve 28 for controlling the direction of fuel flow through the pump outlet passageway 25.

The check valve 28 is of the ball-type and comprises a conical valve seat 29 surrounding the outlet passageway 25 and a ball valve element 30 movable into engagement with the valve seat to close the passageway and movable away from the valve seat in response to fuel pressure exerted thereon to open the passageway. A biasing spring 31 resiliently urges the ball element 30 against the valve seat.

A series of fuel passageways are provided in the main body unit 10 to supply fuel into both the control chamber 12 and the pump chamber 20 and to exhaust fuel from the control chamber 12 in accordance with fluctuating pressure conditions in the engine cylinder C. The fuel passageways include a fuel inlet passageway 35 connectable to a source of fuel during use of the fuel injector assembly through a conventional fitting 36. The inletpassageway 35 branches into a main path 37 which leads into the pump chamber 20 through a check valve .38; and an auxiliary path 40 which leads into the control chamber 12 through another check valve 42. The check valves 38 and 42 are similar in construction to the check valve 28 and function to respectively admit fuel flow from the main inlet passageway 35 into the pump chamber 20 and the control chamber 12 but effectively prevent fuel flow in the reverse direction.

Along the auxiliary fuel path 40 is removably inserted a fuel filter or strainer 43 which is of conventional construction and which functions to filter the fuel as same flows through the fuel injector assembly and before the fuel is spray-injected into the associated engine cylinder. The fuel filter 43 is inserted into the fuel path 40 through a bore 44 which is closed by a threaded plug 45 screwed into the main body unit and the check valve 42 is inserted into a bore 46 which is closed by a threaded plug 47. The bores 44 and 46 comprise a fuel accumulator for storing a quantity of fuel prior to delivering same to the control chamber 12.

A fuel outlet passageway 50 communicates the control chamber 12 with an outlet port 52 and the outlet port is connected to a fitting 53. A hydraulic connection is provided between the fitting 53 and the fuel source and a control valve CV is inserted in the hydraulic connection to control the rate of fuel discharged through the outlet port 52. The control valve CV is mechanically connected to the accelerator pedal of the motor vehicle so that the rate of fuel exiting from the control chamber 12 is controlled in dependence upon the setting of the accelerator pedal. The control valve CV per se is of well known construction and hence will not be further described but a detailed description of the function and operation of the control valve in conjunction with the operation of fuel injector assembly will be described hereinafter.

A modulator valve 55 is disposed in the outlet passageway to modulate the exhausting of fuel from the control chamber 12 to the outlet port 52 in accordance with both the pressure of the fuel temporarily stored in the control chamber 12 and the setting of the control valve CV. The modulator valve 55 comprises a hollow cylindrical valve member 56 having one closed end and one open end and the member is slidably mounted in a cylindrical bore 57. A set of valve ports 58 are arranged circumferentially around the cylindrical valve member 56 and function to provide communication between the control chamber 12 and the outlet port 52 when the valve member 56 is axially shifted along the bore 57 to the position shown in FIG. 2.

A biasing spring 60 normally biases the valve member 56 into the position shown in FIG. 1 and the biasing spring 60 is compressed between the closed end of the valve member and a threaded plug 62 screwed into the main body unit 10. The biasing spring 60 is carefully selected so as to have the necessary spring constant to ensure that the modulator valve 55 correctly modulates the exhausting of fuel from the working chamber 12 in dependence upon the desired fuel pressure built up in the chamber 12 to obtain the proper metering of fuel injected into the engine cylinder C. The biasing force exerted by the spring 60 may be finely adjusted by simply screwing the plug 62 either into or out of the main body unit 10.

The operation of the fuel injector assembly will now be described with reference to FIGS. 1-3. During operation of the motor vehicle, fuel is continuously supplied from a fuel pump (not shown) to the inlet passageway 35 at a constant pressure of about 25 psi. and if necessary, a pressure regulating valvev may be interposed between the fuel pump and the inlet passageway to maintain the fuel pressure at a substantially constant value. The fuel flows along the inlet passageway 35 and into the main path 37 through the check valve 38 into the pump chamber 20 while at the same time branches into the auxiliary path 40 through the check valve 42 ,into the control chamber 12. The fuel injector assembly is primed and ready for use as soon as the control chamber is completely filled with fuel.

For the purpose of describing the operation, it will be assumed that the fuel injector assembly is primed and the components occupy the positions shown in FIG. 1 which depicts that portion of the engine operating cycle wherein the engine piston has just completed its expansion stroke and is ready to commence its compression stroke. As the engine piston moves through its compression stroke, the gaseous mixture in the engine cylinder is compressed to a degree proportional to the volume and density of gas in the engine cylinder as well as the compression ratio of the engine. The gas pressure is continuously applied to the outer face of the piston head 15 since same is always exposed to the environment within the engine cylinder C and as the gas pressure progressively increases during the compression stroke, the force applied to the working piston 13 increases accordingly.

Opposing the force applied to the working piston 13 by the gas pressure is the combined forces exerted on the inner face of the piston head 15 by the biasing spring 17 and by the fuel trapped in the control chamber 12. The check valves 38 and 42 prevent return flow of fuel and thus confine the fuel to the control chamber 12. As the gas pressure applied to the working piston 13 increases due to the movement of the engine piston through its compression stroke, the working piston 13 is urged upwardly with greater force and accordingly pressurizes the fuel trapped in the control chamber 12. The fuel contained within the control chamber 12 is therefore raised in pressure by the pumping action of the working piston 13.

Since the fuel is essentially an incompressible liquid, the fuel does not compress to any significant extent in response to the compressive forces exerted thereon and thus the working piston 13 remains substantially stationary while the fuel pressure rapidly increases during the initial phase of the compression stroke of the engine piston. When the fuel pressure within the control chamber 12 reaches a predetermined value, the fuel pressure acts upon the closed end of the cylindrical valve element 56 and effects movement of the modulat'or valve 55 against the biasing force of the spring 60 so that the valve ports 58 move into registry with the outlet passageway 50 thereby permitting fuel to exhaust from the control chamber 12.

As the fuel exhausts from the control chamber 12, the volume of fuel in the chamber decreases allowing the working piston 13 to be driven upwardly the gas pressure developed in the engine cylinder CJTh'e upward movement of the working piston 13 causes a corresponding upward movement of the pump plunger 22 into the pump cylinder 20 thereby pressurizing the fuel contained within the variable volume pumping chamber and forcing same along the'pump outlet passageway 25 through the check valve 28 and then out the spray nozzle 27 whereby the fuel is injected into theengine cylinder C. The positions of the various components during this stage of the engine operating cycle is shown in FIG. 2.

During the initial upward movement of the pump plunger 23, the radial bore 26 becomes covered by the pump-cylinder wall so that no more than the volume of fuel contained within the pumping chamber is admitted into the engine cylinder C and by such a construction, the fuel injector assembly may readily be adapted to engines having different engine displacements and fuel requirements by simply changing the displacement volume of the fuel injector pump. During downward movement of the pump plunger 22, the radial bore 26 moves away from the pump cylinder wall to permit fuel to flow from the control chamber 12 through the bore 26 into the pump chamber 20 to assist in charging fuel into the pump chamber.

In accordance with the present invention, the modulator valve 55 modulates the exhausting of fuel from the control chamber 12 in dependence upon the magnitude of the fuel pressure in the chamber 12 which in turn is dependent upon the pressure of the gas mixture in the engine cylinder C as developed during the engine piston compression stroke. Therefore, the modulator valve 55 modulates the flow rate of fuel exhausting from the control chamber 12 as a function of the fuel requirements of the engine since, as aforementioned, the gas pressure developed in the engine cylinder depends upon the volume and density of gas in the engine cylinder as well as the compression ratio of the engine. The rate of exhaustion of the fuel from the control chamber 12 determines and controls the pumping stroke of the pump plunger 22 and by doing so, controls both the amount and rate of fuel injected through the spray nozzle 27 into the engine cylinder.

The operation of the modulator valve 55 will now be described in more detail with reference to FIGS. 3A-3C. During the initial upward travel of the working piston 13 during the compression stroke, the fuel within the control chamber 12 is progressively increased in pressure and the fluid pressure acts upon the inner face of the cylindrical valve element 56 causing axial movement of the valve element against the spring .60. When the engine working piston reaches about 40 before top center, the valve element has moved to the position shown in FIG. 3A wherein the valve ports 58 move into partial registry with the outlet passageway 50. Thus fuel begins to flow from the control chamber 12 serially through the valve ports 58, outlet passageway 50, outlet port 52, control valve CV and into the source of fuel.

As the engine working piston continues its upward travel, the fuel pressure rises within the control chamber 12 thereby forcing the valve element 56 to its wide open position, as shown in FIG. 3B, wherein the valve ports 58 are in complete registry with the outlet passageway 50. At this point in the overall operating cycle, the fuel exhausts at the maximum rate from the control chamber 12 and the working piston 13 moves rapidly through its stroke to accordingly drive the pump plunger 22 through its pumping stroke. At this time, the injection of fuel into the engine cylinder C is in full progress.

When the engine working piston nears the end of its upwardtravel, the fuel pressure rises sufficiently to force the valve element 56 to its endmost position, as shown in FIG. 3C, wherein the valve ports 58 are moved completely out of registry with the outlet passageway 50 and fuel no longer discharges from the control chamber 12. The fuel remaining within the control chamber is thus trapped therein and forms a hydraulic lock which effectively prevents further upward movement of the working piston 13 despite further increases in the gaseous pressure in the engine cylinder C. By such an arrangement, the trapped fuel prevents further displacement of the working piston 13 and the pump plunger 22 is thus forced to terminate its pumping stroke and the necessary metered amount of fuel is delivered to the engine cylinder.

The purpose of the control valve CV is to adjustably set the rate of fuel discharge through the outlet port 52 in accordance with the engine requirements. Since the control valve is mechanically linked to the accelerator pedal, the position of the accelerator pedal will accordingly determine the control valve setting and thereby determine the discharging rate of the fuel from the control chamber 12. For each control valve setting, the modulator valve 55 modulates the exhausting of fuel from the control chamber 12 in accordance with the pressure of the fuel temporarily stored within the chamber 12.

An important feature of the present invention is that the amount of fuel delivered to the engine cylinder during each cycle of operation is determined by the stroke length of the pump plunger 22 and the timing of the fuel delivery is determined by the stroke rate of the pump plunger and both of these variables are con trolled by the modulator valve 55. The modulator valve modulates the exhausting of fuel from the control chamber 12 in dependence upon the setting of the control valve CV to thereby control the injection of fuel into the engine cylinder in accordance with varying engine operation conditions. The modulator valve member 56 is axially positioned in accordance with the fuel pressure prevailing in the chamber 12 and effectively modulates the fuel flowing through the valve ports 58 to accurately control the fuel injected into the engine cylinder.

Another important aspect of the present invention is that the control of the fuel is obtained solely in dependence upon the existing engine operating conditions and the fuel injector assembly automatically compensates for variations in air density and various other engine parameters. The fuel injector assembly does not utilize mechanical linkages which are susceptible to sticking or binding and instead, employs hydraulic components which are more reliable and faster acting. Moreover, the operating characteristics of the fuel injector assembly may be selectively varied by replacing the check valve biasing springs and the modulator valve biasing spring with springs having different spring constants and by adjusting the plug 62 to adjust the threshold setting of the modulator valve 55.

FIG. 4 shows another embodiment of fuel injector pump useable in the fuel injector assembly. The injector pump comprises a pump plunger slidably mounted in the pump chamber 20 and the plunger has a cylindrical upper portion 72 and a cylindrical lower portion 73 of larger diameter than the upper portion 72. A conical valve seat 75 is threaded into the interior of the lower portion 73 and a valve needle 76 is movably disposed within lower portion 73 and coacts with the valve seat 75 to control the flow of fuel from the variable volume pumping chamber to the engine cylinder.

An outlet passageway 77 extends through the pump plunger 70 and through both the valve seat and valve needle and terminates in a set of four nozzle jets 78. The nozzle jets 78 are symmetrically arranged around the end tip of the plunger 70 and the jets are dimensioned and angled to dispense the fuel in the form of tiny droplets thereby promoting uniform mixture of the fuel in the air contained within the engine cylinder. A biasing spring 79 urges the movable valve needle 76 against the valve seat 75 to normally close the outlet passageway 77.

The operation of the fuel injector pump shown in FIG. 4 is similar to that of the pump shown in FIGS. 1-2 and during upward movement of the pump plunger 70, the fuel within the variable volume pumping chamber is increased in pressure and exerts sufficient force on the movable valve needle 76 to move same against the biasing spring away from the valve seat 75 to enable the fuel to be injected through the nozzle jets 78.

The embodiment of fuel injecter pump shown in FIG. 5 is generally similar to that shown in FIG. 4 except that the positions of the valve seat and valve needle are reversed. In the FIG. 5 variation, the valve needle 75' is threaded into the valve plunger and the valve seat 76 is movably disposed within the valve plunger. In all other respects, the fuel injector pump is similar to that shown in FIG. 4.

Various modifications of the fuel injector assembly will become apparent to those persons ordinarily skilled in the art and the present invention is intended to cover all such obvious modifications falling within the spirit and scope of the invention'as defined in the appended claims.

What I claim is:

1; A fuel injector assembly for injecting liquid fuel into a combustion zone comprising: means defining a variable volume control chamber including a movable working member movable in one direction to diminish the volume of said control chamber and movable in an opposite direction to increase the volume of said control chamber and mountable during use of the fuel injector assembly such that said working member is in direct communication with the combustion zone; fuel injecting means connected to said working member and movable therewith for injecting liquid fuel into the combustion zone in an amount and at a rate proportional to the extent and rate of movement of said working member in said one direction; biasing means for continuously biasing said working member in said opposite direction; means for supplying liquid fuel into the interior of said control chamber thereby preventing movement of said working member in said one direction due to the incompressible nature of the liquid fuel; and modulator valve means responsive to the fuel pressure in said control chamber for modulating the exhausting of fuel from said control chamber as a function of the pressure exerted on said working member from the combustion zone to thereby control the rate and extent of movement of said working member in said one direction to accordingly control the timing and amount of fuel injected into the combustion zone; said fuel injecting means comprising means defining a variable volume pumping chamber including a pump plunger connected to said working member and movable therewith to vary the volume of said pumping chamber, means for supplying liquid fuel into said pumping chamber during movement of said working member in said opposite direction, means defining a pump outlet passageway extending longitudinally through said pump plunger from said pumping chamber into the combustion zone, and check valve means mounted in said pump outlet passageway operable to permit fuel flow therethrough in a direction from said pumping chamber into the combustion zone but not in the reverse direction; said means for supplying liquid fuel into said pumping chamber includes means defining a bore extending transversely through a portion of said pump plunger providing communication between said outlet passageway and the interior of said control chamber when said pump plunger is at the end of its stroke after moving inthe opposite direction to admit fuel into said pumping chamber from said control chamber, and wherein said pumping chamber has a wall portion which covers said bore to prevent further fuel admission therethrough after said pump plunger has moved a predetermined distance from the end of said stroke in said one direction.

2. A fuel injector assembly for injecting'liquid fuel into a combustion zone comprising: meansdefining a variable volume control chamber including a movable working member'movable in one direction to diminish the volume of said control chamber and movable in an opposite direction to increase the volume of said control chamber and mountable during useof the fuel in-' jector assembly such that said working member is in direct communication with the combustion zone; fuel injecting means connected to said working member and movable therewith for injecting liquid fuel into the combustion zone in an amount and at a rate proportional to the extent and rate of movement of said working member in said one direction; biasing means for continuously biasing said working member in said opposite direction; means for supplying liquid fuel into the interior of said control chamber thereby preventing movement of said working member in said one direction due to the incompressible nature of the liquid fuel; and'modulator valve means responsive to the fuel pressure in said control chamber for modulating the exhausting of fuel from said control chamber as a function of the pressure exerted on said working member from the combustion zone to thereby control the rate and extent of movement of said working member in said one direction to accordingly control the timing and amount of fuel injected into the combustion zone; said modulator valve means comprises means defining an outlet port connectable during use of the fuel injector assembly to a source of fuel, an exhaust passageway providing communication between said outlet port and said control chamber, a pressure-responsive modulator valve element slidably mounted within said exhaust passageway and having means therein for selectively providing communication between said outlet port and said control chamber in dependence upon the position of said valve element, and biasing means for normally biasing said valve element into a position wherein same does not provide communication between said outlet port and said control chamber thereby normally preventing the fuel from exhausting from said control chamber and permitting sliding movement of said valve element against the force exerted by said biasing means to provide communication between said outlet port and said control chamber in response to fuel pressure applied to said pressure-responsive modulator valve element; said pressure-responsive modulator valve elemerit comprises a hollow cylindrical valve element havsaid cylindrical valve element for providing communiing a closed end defining a pressure-acting surface cation between said outlet port and said control chamupon which the fuel pressure acts, and means defining ber.

21 set of valve ports disposed circumferentially around 

1. A fuel injector assembly for injecting liquid fuel into a combustion zone comprising: means defining a variable volume control chamber including a movable working member movable in one direction to diminish the volume of said control chamber and movable in an opposite direction to increase the volume of said control chamber and mountable during use of the fuel injector assembly such that said working member is in direct communication with the combustion zone; fuel injecting means connected to said working member and movable therewith for injecting liquid fuel into the combustion zone in an amount and at a rate proportional to the extent and rate of movement of said working member in said one direction; biasing means for continuously biasing said working member in said opposite direction; means for supplying liquid fuel into the interior of said control chamber thereby preventing movement of said working member in said one direction due to the incompressible nature of the liquid fuel; and modulator valve means responsive to the fuel pressure in said control chamber for modulating the exhausting of fuel from said control chamber as a function of the pressure exerted on said working member from the combustion zone to thereby control the rate and extent of movement of said working member in said one direction to accordingly control the timing and amount of fuel injected into the combustion zone; said fuel injecting means comprising means defining a variable volume pumping chamber including a pump plunger connected to said working member and movable therewith to vary the volume of said pumping chamber, means for supplying liquid fuel into said pumping chamber during movement of said working member in said opposite direction, means defining a pump outlet passageway extending longitudinally through said pump plunger from said pumping chamber into the combustion zone, and check valve means mounted in said pump outlet passageway operable to permit fuel flow therethrough in a direction from said pumping chamber into the combustion zone but not in the reverse direction; said means for supplying liquid fuel into said pumping chamber includes means defining a bore extending transversely through a portion of said pump plunger providing communication between said outlet passageway and the interior of said control chamber when said pump plunger is at the end of its stroke after moving in the opposite direction to admit fuel into said pumping chamber from said control chamber, and wherein said pumping chamber has a wall portion which covers said bore to prevent further fuel admission therethrough after said pump plunger has moved a predetermined distance from the end of said stroke in said one direction.
 2. A fuel injector assembly for injecting liquid fuel into a combustion zone comprising: means defining a variable volume control chamber including a movable working member movable in one direction to diminish the volume of said control chamber and movable in an opposite direction to increase the volume of said control chamber and mountable during use of the fuel injector assembly such that said working member is in direct communication with the combustion zone; fuel injecting means connected to said working member and movable therewith for injecting liquid fuel into the combustion zone in an amount and at a rate proportional to the extent and rate of movement of said working member in said one direction; biasing means for continuously biasing said working member in said opposite direction; means for supplying liquid fuel into the interior of said control chamber thereby preventing movement of said working member in said one direction due to the incompressible nature of the liquid fuel; and modulator valve means responsive to the fuel pressure in said control chamber for modulating the exhausting of fuel from said control chamber as a function Of the pressure exerted on said working member from the combustion zone to thereby control the rate and extent of movement of said working member in said one direction to accordingly control the timing and amount of fuel injected into the combustion zone; said modulator valve means comprises means defining an outlet port connectable during use of the fuel injector assembly to a source of fuel, an exhaust passageway providing communication between said outlet port and said control chamber, a pressure-responsive modulator valve element slidably mounted within said exhaust passageway and having means therein for selectively providing communication between said outlet port and said control chamber in dependence upon the position of said valve element, and biasing means for normally biasing said valve element into a position wherein same does not provide communication between said outlet port and said control chamber thereby normally preventing the fuel from exhausting from said control chamber and permitting sliding movement of said valve element against the force exerted by said biasing means to provide communication between said outlet port and said control chamber in response to fuel pressure applied to said pressure-responsive modulator valve element; said pressure-responsive modulator valve element comprises a hollow cylindrical valve element having a closed end defining a pressure-acting surface upon which the fuel pressure acts, and means defining a set of valve ports disposed circumferentially around said cylindrical valve element for providing communication between said outlet port and said control chamber. 